1. Field of the Invention
The invention generally relates to a light source module, and more particularly, to an illumination apparatus using the light source module.
2. Description of Related Art
In a side-type backlight module employing light emitting diodes (LEDs) as the light-emitting devices thereof, a plurality of LEDs arranged in a line with an interval are disposed beside a light incident surface at a side of a light guide plate (LGP) thereof. Light beams provided by the LEDs enter the LGP through the light incident surface of the LGP. The light beam of the LEDs has higher directionality, i.e., each of the LEDs has a specific light exiting angle range, so that a bright region is formed in an area of the LGP, wherein the area is close to the LED and falls in the light exiting angle range of the LED, while meantime, a dark region is formed in another area out of the light exiting angle range. The bright regions and the dark regions make the planar light source provided by the LGP ununiform to produce so-called hot spot phenomena. In order to reduce the influence of the hot spot phenomena, an area from the light incident side of the LGP to a place far away from the light incident side is used as a light-blending area for the light beams of the LEDs after entering the LGP. As a result, the area of the light exiting surface of the LGP able to provide an effective planar light source is reduced.
Although an increased quantity of the LEDs is able to effectively reduce the hot spot phenomena and shorten the distance of the light-blending area, however, increasing the quantity of the LEDs would increase the cost and the overall temperature leading to a shorter LED lifetime. In general speaking, when the ratio (A/P) of the light-blending distance of the light-blending area (A) over the interval between two adjacent light-emitting devices (P) gets less, the hot spot phenomena get more unnoticeable. According to the design currently, the ratio (A/P) of the light-blending distance of the light-blending area (A) over the interval between two adjacent light-emitting devices (P) is about 1.7, no way to make A/P less.
U.S. Pat. No. 6,874,900 discloses a direct-type backlight module, wherein the backlight module includes an LGP and a plurality of LED light sources. The LGP further includes a plurality of dents and a plurality of concave portions, wherein the dents are for accommodating the LED light sources and each dent includes a horizontal surface, a turncate conic surface, and a vertical wall.
Taiwan Patent No. I285286 discloses a direct-type backlight module, and the direct-type backlight module includes an LGP and an LED light source. The LGP therein further includes an insertion portion and a conic concave portions, wherein the LED light source is disposed in the insertion portion, and the tangent slopes of the light exiting area of the LED light source are similar to the corresponding tangent slopes of the insertion portion, i.e., the shape of the LED light exiting area is conformed to the insertion portion. By using the design, the light beam from the light exiting area of the LED light source after being transmitted to the insertion portion would be directly and perpendicularly incident on the insertion portion, and the light beam would be directly transmitted to the light exiting surface, not be refracted with a larger angle to enter the LGP and not be continuously transmitted. As a result, the light intensity near to the insertion portion and the conic concave portions would be more concentrative, which makes the light intensity distribution in the LGP more ununiform.
Taiwan Patent No. M331679 discloses a side-type backlight module, and the side-type backlight module includes an LGP and a light source module, wherein a light-emitting area of the light source module covers a light incident surface of the LGP. In addition, the light source module includes a plurality of LEDs, two correction bodies, and a reflective plate, wherein the two correction bodies respectively have a light-guiding surface, a light exiting surface, and a reflection surface, and the two correction bodies are disposed in leaning against each other.